Thermocopying machine

ABSTRACT

A thermocopying machine having an endless belt on which the copying set consisting of an original and a copy sheet is carried past a rod shaped infrared radiator. The belt is provided with holding means which are arranged to resist displacements of the leading and trailing edges of the copying set relative to the belt during the passage of the set through a curved section of the path opposite the radiator. The force with which said displacements are resisted is at least partly converted into radially directed contact pressure between the original and the copy sheet.

United States Patent Laursen [151 3,687,551 Aug. 29, 1972 [54] THERMOCOPYING MACHINE [7 2] Inventor: Ejnar Munk Laursen, Adiget 18,

2610 Rodovre, Denmark [22] Filed: March 24, 1970 [21] Appl. No.: 22,346

[30] Foreign Application Priority Data March 24, 1969 Denmark ..1605/69 [52] US. Cl. ..355/ll0, 250/65 T [51] Int. Cl. ..G03b 27/10 [58] Field of Search ..355/91, 104,111,117, 108,

[56] References Cited UNITED STATES PATENTS 8/1965 Thomiszer ..250/65 T Creange ..355/117 Miller et a1 ..250/65 T R22,575 l2/l944 2,958,778 11/1960 3 ,465, l 22 9/ 1969 Kolless ..250/ 65 T 777,097 12/1904 Herman .,...355/l17 2,522,804 9/1950 Shore ..355/l17 Primary Examiner-Samuel S. Matthews Assistant Examiner-Michael L. Gellner Attorney-Fleit, Gipple & Jacobson [57] ABSTRACT 12 Claims, 5 Drawing-Figures PAIENTEDA H Z 3.681.551

SHEET 1 OF 2 INVENTORS Ejna r Mank Laursen THERMOCOPYING MACHINE For the reproduction of graphic matter such as typed text, drawings or pictures, various types of copy material are known and used, and various requirements therefore have to be complied with in the copying machines employed for the purpose. A frequently used type of paper is thermopaper, which is coated with a thin layer of material that changes color when heated. Another commonly used type is melt paper, which is coated with a colored mass that melts when heated and can be transferred by pressure to another sheet material such as paper or fabric. The colored mass may for example be soluble in spirit and the produced reversed copy is used as master in a spirit duplicator. A third, relatively new type of copy material is a so-called thermostencil, which has a thin plastics coating in which a certain inner tension is produced which causes the plastics layer to rupture when heated and withdraw from the heated region which is defined by a small bead and in a duplicator ink may then be pressed through the finemeshed netting formed by the bared paper fibers. The known art also comprises thermostencils functioning on basis of melting.

Of the types of paper mentioned by way of example above the melt paper requires a relatively high pressure between the master and the copy sheet, whereas such a high pressure would be inimical to a therrnostencil because it would prevent the plastics layer functioning properly. Thermopaper requires mere contact between master and copysheet, but can stand a higher pressure.

The most frequently used thermocopying machines may be divided into two types: glass tube machines and belt machines. Both employ a rod-shaped heat radiator and a reflector which concentrates the infrared rays in a relatively narrow band across the advancing copy material.

In the glass tube machine the master and copy material are passed under pressure in between a rubber roller and a glass cylinder enclosing the heat radiator. This machine is unfit for paper that cannot stand pressure. Besides, the glass tube cannot without considerable costs be made perfectly cylindrical and free of foreign matter or optical blemishes which might cause variations in the radiation intensity. Furthermore, the glass will absorb part of the radiated heat and heat both the copy material and the rubber roller by convection. This heating of the copy material will blur the contours by reducing the contrast between the regions to be heated and those that are not to be heated, and, besides, the rubber roller must be of a specifically heatresistant quality.

In the belt machine the master and the copy material are contacted by being passed in between a plastics belt and a metal roller. In this machine it is difficult to maintain a sufficiently high contact pressure belt and roller to produce spirit masters. From a thermo-technical point of view the machine is preferable to the glass tube machine because the roller is of metal and the belt is of a certain length, so that a heated region may cool down before it is again contacted with the copy material.

Both of the said machines require regular cleaning of interior parts to produce satisfactory copies.

This invention relates to a thermocopying machine of the type having an endless belt on which the copy material is carried past a rod-shaped heat radiator disposed opposite a curved section of the belt path, and it is the aim of the invention to provide a machine in which the contact pressure between the original and the copy sheet can be adjusted to requirement and which also possesses good thermo-technical properties.

This aim has been accomplished by providing the belt with holding means adapted to retain the copy material directly or indirectly on the belt by a force adjusted to the desired printing pressure between the original and the copy sheet so as to resist displacement of the end edges of the copy material relatively to the belt in the longitudinal direction thereof which the belt traverses the said curve section of its path. While the belt traverses a curved section of its path the copy material will get a slightly greater radius of curvature than the belt and therefore tend to be displaced longitudinally relatively to the belt, and this displacement is prevented or resisted by the holding means and converted wholly or partly to tension in the copy material which will tend to urge the original and the copy sheet against each other and against the belt.

The surface pressure produced in this manner will be determined by various factors such as the radii of curvature of the belt path and the copy material, the physical properties of the copy material, the angle of contact, i.e. the angle between the radii to the two extreme points of the curved section of the path, and the degree of elasticity in the attachment means connecting the copy material and the belt, and the contact pressure between the original and the copy sheet may thus be varied by adjustment of one or more of these factors.

The relatively long path over which a heated section of the belt travels before it is again exposed to the heating of the radiator affords good possibilities of cooling down.

In a simple construction of the copying machine which can be used with all kinds of thermocopying processes the holding means is a cover sheet connected along one end edge rigidly or resiliently to the belt while its other end edge is adapted to be detachably connected to the belt. In this manner the contact pressure between the original and the copy sheet will be determined by the tension in the cover sheet and a high contact pressure can be provided without special requirements to the physical strength of the copy sheet.

The front edge of the cover sheet may conveniently be attached to a rail connected to the belt by resilient means, the end portions of the rail being connected to their respective ends of a transversely extending leaf spring, the central portion of which is attached to the belt, and the action of which may be limited by stop means provided on the belt. The edge portions of the belt may travel over two pairs of reels, the two reels of each pair being mounted coaxially. Thus structural elements may be disposed on the inner surface of the belt and pass freely between the two reels of a pair with the travelling of the belt. The leaf spring, for instance, may be mounted on the inner surface of the belt and connected to the rail by cords passed through apertures in the belt.

The holding means at the rear edge of the cover sheet may expediently be provided in the form of hooks adapted for engagement with apertures in the belt, and to reinforce theedges of the apertures in the relative thin belt against the often rather heavy action of the hooks a transversely extending reinforcing rail may be provided on the inner surface of the belt along the front edges of the apertures.

An even distribution of the contact pressure between the master and the copy sheet may be provided by a resilient pad on the belt serving as support for the copy material, and to obviate the difficulties that might be caused by friction between the resilient pad and the copy material and impede the necessary relative movement of these members a sheet material having a low coefficient of friction may be disposed on the pad and secured to the belt along one end edge.

If the machine is to be used chiefly for the production of thermostencils, which do not require any contact pressure between the original and the copy sheet, the cover sheet may be dispensed .with and its blurring effect avoided, and in that case at least one of the holding means may be a transverse clip connected fixedly or releasably to the belt.

Particularly good thermal conditions may be obtained by using a metal belt and positioning the heat radiator opposite a curved section of the travelling path of the belt.

If the machine is to be used with copying processes that involve so high contact pressures between the original and the copy sheet that they exceed the capacity of the holding means the heat radiator may be enclosed in a hollow counter-pressure roller made from a material which is permeable to infrared rays, and at least the reels adjacent to the heat radiator are then provided with a circular flange the radial height of which from the cylindrical contact face between the reels and the belt is less that the thickness of the resilient pad without copy material thereon, the end portions of the counter-pressure roller being maintained in engagement with these flanges. This obviates the drawbacks experienced in the known machines using glass tubes, where irregularities in the shape of the glass tube may cause variations in the distance between heating rays and copy material and thus affect the quality of the produced copies.

The invention will be explained in greater detail here with reference to the drawing, in which FIG. 1 presents a schematic view of an embodiment of the copying machine according to the invention,

FIG. 2 is a somewhat schematized longitudinal section through part of the belt of the machine with the individual components of the holding means drawn apart,

FIG. 3 is a corresponding section showing the copy material disposed on the belt and the holding means in their proper places,

FIG. 4 shows part of an amended embodiment of the machine according to the invention viewed in perspective and partly in section, and

FIG. 5 presents a section along the line V--V in FIG. 4.

The thermocopying machine illustrated in FIG. 1 comprises a belt 1 of metal, for instance steel or phosphor-bronze, travelling over two pairs of reels 2 and 3, the two reels of each pair being mounted co-axially and engaging opposed edges of the belt. Onto the outer surface of the belt is glued a resilient pad 4, for instance of rubber and serving as support for the copy material. The copy material is held in position by means of a cover sheet 5 which is secured to the belt in a manner that will be described later in the explanation of FIGS. 2 and 3. An electromotor (not shown here) drives one reel pair 2 in the direction indicated by an arrow, whereby the copymaterial will be caused to travel closely past a rod-shaped heat radiator 6 provided with a reflector 7 formed as a cylinder surface and concentrating the infrared rays in a narrow band across the copy material.

The cover sheet 5 may, for instance, be made from glass fiber reinforced teflon, which is heat resistant and yield but low resistance to the passage of infrared rays. As indicated in FIGS. 2 and 3, the front edge of this cover sheet is retained between two metal rails 8 and 9 held together by means of screws 10 extending through plain holes in the upper rail 8 and into threaded holes in the lower rail 9. These rails are of arcuate cross section with a radius of curvature corresponding to the reels 2 and 3. On the lower rail 9 is disposed guide pins 11 extending upwardly through apertures in the cover sheet 5 and in the upper rail 8.

The side edges of a strip 12, which may for instance be of glass fiber reinforced teflon, are also clamped between the rails 8 and 9, this strip forming a transverse channel in which a bent metal bar 13 of arcuate cross section is mounted.

On the under surface of the belt 1 is attached a transversely extending angle iron 14, for instance by means of screws, which are not shown here. To the vertical flange of the angle iron is secured the central section of two leaf springs 15 and 16, shaped as flat Vs of slightly different angles between the legs. Adjacent to each end of the rail 13 is attached a Bowden cable 17 which has been passed through an aperture in the belt 1 and from there through apertures in the vertical flange of the angle iron 14 and in the ends of the springs 15 and 16. At the free end of each Bowden cable is provided a sleeve 18 which by means of a screw can be secured at any desired point of the cable.

The rear edge portion of the cover sheet 5 is folded to form a transverse channel in which is disposed a rail 19 similar to the rail 13 but provided with a plurality of longitudinally spaced hooks 20 projecting through apertures in the channel-forming portion of the cover sheet 5. These hooks are adapted to retain. the rear edge of the cover sheet relatively to the belt 1 by being carried downwards into their respective apertures 21 in the belt. To avoid tearing of the edges of the apertures they have been reinforced by a rail 22 disposed on the under surface of the belt, the edge of the rail adjacent to the apertures 21 forming an acute angle with the belt.

The rear edge of a base sheet 26 extending forwardly over the resilient pad 4 is secured a short distance behind the pad by means of a rail 23 similar to the rail 13 and screws 24 extending into threaded holes in a transverse rail 25 disposed on the under surface of the belt. The said base sheet may, like the cover sheet 5, be of glass fiber reinforced teflon, which besides its good thermal properties also possesses high tensile strength and low coefficient of friction and therefore slides readily on the pad 4.

When a document is to be copied the rear portion of the cover sheet 5 is raised, the document and a copy sheet are disposed on the base sheet 26, and the hooks 20 of the cover sheet are inserted in the apertures 21 in the belt 1, as shown in FIG. 3, in which the document or original is designated 27 and the copy sheet 28. During this process the sleeves 18 on the Bowden cable 17 are drawn against the ends of the outermost spring 15 tensioning it to a degree determined by the location of the sleeves on the cables. The tension in the cover sheet may therefore be regulated by adjustment of the sleeves 18.

When the sheet material during operation pass downwards over the reels 2, the sheets are caused to follow an arcuate path which, on account of the thickness of the pad 4 and the sheets themselves, has a greater radius of curvature than the belt. This results in a further tensioning of the spring 15 and possibly also a tensioning of the spring 16 and the resulting tensile stress in the cover sheet 5 will produce the desired contact pressure between the original 27 and the copy sheet 28 in the region where the copying operation occurs, namely opposite the heat radiator 6, 7. The base sheet acts as lubricant permitting relative movement between the copy material 27,28 and the pad 4. Without this base sheet there would be a risk of the friction between the pad 4 and the copy material preventing the copy material straigthening out after the passage of the curved sections of the path so that folds might be formed in the copy material.

In the example described above the original 27 was placed lowermost so that the heat radiation is performed through the copy sheet; but in some thermocopying processes it is more convenient to place the copy material on top so that the radiation is effected through the original.

When using copying processes that require no contact pressure but mere contact between the original and the copy sheet it may be convenient to retain the copy. material on the belt in other ways than by means of the cover sheet 5, in order to avoid the heat loss involved thereby. This, for instance, is the case in the production of thermostencils. When the machine is to be used for this purpose, the cover sheet 4 may be dismantled by removing the screws and the rail 8, and by means of the apertures in the front edge of the thermostencil the stencil may be fitted on the pins 11 of the rail 9. The rear edge of the stencil may be retained for instance by means of a spring-loaded clip (not shown here), which may be mounted permanently on the belt or be secured detachably, for instance by means of books adapted for engagement with the apertures 21.

In order to improve the quality of copying work that requires a very high contact pressure between the original and the copy sheet, the machine may be provided in a manner known per se with a hollow counterpressure roller enclosing the heat radiator 6,7 and made from a material that is permeable to infrared rays, such as for instance glass. A machine like this is illustrated scematically in FIGS. 4 and 5, in which the counter-pressure roller is designated 29. In this construction the reels 2 are provided with a circular flange 30, the radial depth d of which from the cylindrical belt contact face of the reels is somewhat less than the thickness t of the resilient pad 4 without sheet material thereon. The counter-pressure roller 29 is maintained in abutment against these flanges 30 by spring-loaded pressure rolls 31. When the pad 4 and the copy materia1 placed thereon and the holding means therefor (for the sake of lucidity not shown in FIGS. 4 and 5) travel downwards between the reels 2 and the counter-pressure roller 29, the pad will be compressed so much that the roller 29 will remain all the time in contact with the flanges 30, as indicated most clearly in FIG. 5, and despite possible irregularities in the form of the counter-pressure roller the distance between the copy material and the heat radiator 6,7 will always be determined solely by the position of the flanges relatively to the heat radiator and therefore be independent of such irregularities.

Many other modifications of the illustrated and explained construction will be possible within the scope of the invention. The belt 1, for instance, may be of a suitable plastics material instead of metal, and all parts of the holding means for the copy material may be mounted on the outer surface of the belt so that the inner surface will be entirely free of projecting members and the belt may travel over two cylindrical rollers instead of two pair of reels.

What I claim is:

1. A thermocopying machine having an endless belt on which the copy material is carried past a rod-shaped heat radiator disposed opposite a curved section of the belt path, characterized in that the belt is provided with holding means in the form of a cover sheet fixedly mounted thereon and moveable therewith, adapted to overlie and retain the copy material relative to the belt in the longitudinal direction thereof while simultaneously increasing printing pressure between the original and the copy sheet to a desired level during the passage of the curved section of the belt path.

2. A thermocopying machine according to claim 1, characterized in that the a cover sheet is connected along one end edge to the belt and wherein the other end edge is adapted to be detachably connected to the belt.

3. A thermocopying machine according to claim 2, characterized in that the front edge of the cover sheet is attached to a rail connected to the belt by resilient means.

4. A thermocopying machine according to claim 3, characterized in that the end portions of the rail are connected to respective ends of a transversely extending leaf spring, the central portion of which is attached to the belt.

5. A thermocopying machine according to claim 4, characterized in that the belt is provided with stop means so positioned as to limit the deflection of the leaf spring by being engaged thereby.

6. A thermocopying machine according to claim 4, characterized in that the leaf spring is disposed on the inner surface of the belt and connected to the rail by cords passed through apertures in the belt.

7. A thermocopying machine according to claim 2, characterized in that hooks are provided at the rear edge of the cover sheet adapted for engagement with apertures in the belt.

8. A thermocopying machine according to claim 7, characterized in that a transversely extending reinforcing rail is provided on the inner surface of the belt along the front edges of the apertures in the belt adapted to receive the hooks.

belt travel over two pairs of coaxial reels, characterized in that at least the reels adjacent to the heat radiator are provided with a circular flange the radial height of which from the cylindrical contact face between the reels and the belt is less than the thickness of the resilient pad without sheet material thereon, and that the end portions of the counter-pressure roller are maintained in engagement with these flanges.

12. A thermocopying machine according to claim 1, characterized in that at least one of the holding means is a transverse clip connected to the belt.

UNITED STATES PATENT QFFEGE HFICATEE Q? EQWN Patent No. 3,687,551 Dated August 29, 1972 Invent r( EJNAR MUM" LAURSEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

on the I title page, insert [7 3] Assignee; MEMOFAX A/S Copenhagen, Denmar (SEAL) Attest:

EDWARD M.PLETCHER,JR.

7 ROBERT GOTTSCHALK Attestlng Officer Commissioner of Patents FORM PO-TOSO (10-69) uscoMM-oc 60376-P69 U.S4 GOVERNMENT PRINTING OFFICE: 1959 0-366-334 mitt STATES- PATENT @FFECE r 1 QER'HFEQATE @f toammiiow Patent No- 87, 51 Dated August 29, 1972 Inventor(s) EJNAR MUNK LAURSEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as Shown below:

on the title page, insert [73] Assignee; MEMOFAX A/S Copenhagen, Denmark Signed and sealed this 3rd. day of April 1973.

(SEAL) Attest:

EDWARD M FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60376-P69 k u.s. GOVERNMENT PRINTING OFFICE: 1965 0-355-334 

1. A thermocopying machine having an endless belt on which the copy material is carried past a rod-shaped heat radiator disposed opposite a curved section of the belt path, characterized in that the belt is provided with holding means in the form of a cover sheet fixedly mounted thereon and moveable therewith, adapted to overlie and retain the copy material relative to the belt in the longitudinal direction thereof while simultaneously increasing printing pressure between the original and the copy sheet to a desired level during the passage of the curved section of the belt path.
 2. A thermocopying machine according to claim 1, characterized in that the a cover sheet is connected along one end edge to the belt and wherein the other end edge is adapted to be detachably connected to the belt.
 3. A thermocopying machine according to claim 2, characterized in that the front edge of the cover sheet is attached to a raIl connected to the belt by resilient means.
 4. A thermocopying machine according to claim 3, characterized in that the end portions of the rail are connected to respective ends of a transversely extending leaf spring, the central portion of which is attached to the belt.
 5. A thermocopying machine according to claim 4, characterized in that the belt is provided with stop means so positioned as to limit the deflection of the leaf spring by being engaged thereby.
 6. A thermocopying machine according to claim 4, characterized in that the leaf spring is disposed on the inner surface of the belt and connected to the rail by cords passed through apertures in the belt.
 7. A thermocopying machine according to claim 2, characterized in that hooks are provided at the rear edge of the cover sheet adapted for engagement with apertures in the belt.
 8. A thermocopying machine according to claim 7, characterized in that a transversely extending reinforcing rail is provided on the inner surface of the belt along the front edges of the apertures in the belt adapted to receive the hooks.
 9. A thermocopying machine according to claim 1, characterized in that a resilient pad is provided on the belt to form a copy material support for ensuring an even distribution of said desired printing pressure.
 10. A thermocopying machine according to claim 9, characterized in that a sheet of material having a low coefficient of friction is disposed on said resilient pad.
 11. A thermocopying machine according to claim 9, wherein the heat radiator is enclosed within a hollow counter-pressure roller made of a material permeable to infrared rays, and wherein the edge portions of the belt travel over two pairs of coaxial reels, characterized in that at least the reels adjacent to the heat radiator are provided with a circular flange the radial height of which from the cylindrical contact face between the reels and the belt is less than the thickness of the resilient pad without sheet material thereon, and that the end portions of the counter-pressure roller are maintained in engagement with these flanges.
 12. A thermocopying machine according to claim 1, characterized in that at least one of the holding means is a transverse clip connected to the belt. 